Pumps are commonly used for a wide variety of different applications. Common conventional varieties of pump include positive displacement pumps (such as those comprising a reciprocating piston in a cylinder) and non-positive displacement pumps (such as those comprising centrifugal impellers which fling fluid into a diffusing passageway).
Conventional centrifugal fluid pumps employ a rotating impeller that draws in fluid (for instance, water or air) before ejecting the fluid at high speed from the tips of the impeller blades into one or more diffusing passageways. The purpose of the diffusing passageways is to reduce the high kinetic energy imparted to the fluid by the impeller. This is achieved through providing the diffusing passageways with a progressively increasing cross sectional area that causes the fluid to decelerate in a controlled manner. As fluid speed decreases, an increase in static pressure takes place.
This increase in static pressure is required in many pump applications in order to overcome downstream resistance to the flow of fluid caused by fluid drag against pump walls, surfaces, bends, cross-sectional area changes or introduced elements such as filters.
These conventional pumps suffer from a number of significant disadvantages. Firstly, the impeller flings fluid (such as water) off the tips of the blades into the diffusing passageways but not does force it into the diffusing passageways. This means that the diffuser inlets must be placed close to the blade tips so that the fluid velocity is as high as practical as the fluid enters the passageways. This arrangement results in wake collisions which generate a significant amount of noise.
Another disadvantage of conventional pumps is that, due to a large number of cross-sectional area changes through the passageways within the impeller, casing and pump body, the velocity of the fluid changes repeatedly as the fluid moves through the pump. These velocity changes generally result in a decrease in fluid momentum, meaning that additional power input is required to compensate for the loss in fluid momentum, resulting in a reduction in the efficiency of the pump.
A further disadvantage of conventional pumps is the significant cost of manufacturing the one or more diffusing passageways that are integral to conventional centrifugal pumps.
Thus, there would be an advantage if it were possible to provide a fluid pump that reduced or eliminated at least some of the inefficient design features of conventional centrifugal fluid pumps, thereby providing a pump having improved efficiency and reduced noise.
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